Peralta Genomics Institute, Chancellor's Office, Peralta Community College District, 333 East 8th Street, Oakland, CA, 94606, USA.
AIT Austrian Institute of Technology, Center for Health and Bioresources, Molecular Diagnostics, Giefinggasse 4, 1210, Vienna, Austria.
Commun Biol. 2021 Jan 29;4(1):116. doi: 10.1038/s42003-020-01639-0.
Animal mitochondrial genomic polymorphism occurs as low-level mitochondrial heteroplasmy and deeply divergent co-existing molecules. The latter is rare, known only in bivalvian mollusks. Here we show two deeply divergent co-existing mt-genomes in a vertebrate through genomic sequencing of the Tuatara (Sphenodon punctatus), the sole-representative of an ancient reptilian Order. The two molecules, revealed using a combination of short-read and long-read sequencing technologies, differ by 10.4% nucleotide divergence. A single long-read covers an entire mt-molecule for both strands. Phylogenetic analyses suggest a 7-8 million-year divergence between genomes. Contrary to earlier reports, all 37 genes typical of animal mitochondria, with drastic gene rearrangements, are confirmed for both mt-genomes. Also unique to vertebrates, concerted evolution drives three near-identical putative Control Region non-coding blocks. Evidence of positive selection at sites linked to metabolically important transmembrane regions of encoded proteins suggests these two mt-genomes may confer an adaptive advantage for an unusually cold-tolerant reptile.
动物线粒体基因组多态性表现为低水平的线粒体异质性和深度分歧的共存分子。后者很少见，仅在双壳类软体动物中被发现。在这里，我们通过对唯一代表古老爬行动物目——楔齿蜥（Sphenodon punctatus）的基因组测序，展示了一种脊椎动物中的两个深度分歧的共存线粒体基因组。这两个分子是通过短读长和长读长测序技术的组合揭示的，其核苷酸差异为 10.4%。单条长读长可以覆盖两条链的整个 mt 分子。系统发育分析表明，这两个基因组之间存在着 700 到 800 万年的分歧。与早期的报告相反，所有 37 个动物线粒体典型基因，包括剧烈的基因重排，都在两个 mt 基因组中得到了确认。同样是脊椎动物所特有的，协同进化驱动了三个近乎相同的假定控制区非编码区。与编码蛋白代谢重要跨膜区域相关的位点上的正选择证据表明，这两个 mt 基因组可能为这种异常耐寒的爬行动物提供了适应优势。
